The Complete Online Guide to Knifemaking, BEVEL GRINDING
For the purpose of this online guide, we are going to discuss how to grind flat, hollow, and full-flat bevels. Variations of the above can be attempted after the basics are mastered. When using a belt grinder, always try to do the majority of rough grinding with a coarse grit belt. Coarse grit belts like 36-grit move material fast and generate much less heat than finer grit belts do. Remember to keep a quench tank full of water close by and frequently cool off the work piece. This is especially important when grinding after heat treating when you do not want any excess heat to ruin the temper of the blade. Rough bevels are ground prior to heat treating with a coarse grit belt. After the blade is heat treated and tempered, bevels can be cleaned up or finished ground with a finer belt.
Please note that flat bevels can also be created with simple tools like files. If files are going to be used, try to make up a filing jig that helps to hold the angle of the file consistent. The file jig is really just a board that the knife blank can get clamped to. On the other end is an adjustable height eye bolt. The file is attached to a shaft and inserted through the eye bolt. The height of the bolt is then adjusted to the desired bevel angle. Using a file takes time but getting good results is possible.
An angle grinder and flap sanding wheel can also be used to make the process a little faster. This type of grinder will work better for creating convex bevels on blades designed without a plunge line (cleavers for example). Clamp the blank down to a work table. For blades with a plunge line, use a combination of the disc grinder to remove the bulk of the material and a file to clean up the plunge line. Mark out the height of the desired bevels and plunge line on the blade with a marker or Dykem blue. Stay away from the plunge line with the sanding wheel and attempt to evenly grind away material down to the first center scribe railroad track line. Then, go back with a file and clean up the plunge and bevel line trying to merge the plunge line to the disc grinder created bevel. You can also clamp a bevel plunge jig over the knife which will prevent accidental grinding beyond the planed plunge line. Both of these methods will work but grinding the bevels on a 2x72 grinder is much faster and more accurate.
Grinding Flat Bevels
Grinding good bevels is a true art in itself. Many knifemakers have major problems grinding clean straight bevels. First off, understand that there are many ways to grind bevels. Freehand grinding is the hardest to master. Freehand grinding is a skill only learned by trial and error. Most say to hold your elbows in tight against your body, support the blade edge up so you can visualize the railroad track scribed center lines. Hold the blade at a sharp angle and then slowly start to remove material. The object is to break the edge and then change the angle and slowly chase the bevel ridge upward until the desired width is reached. After each pass take a look at the grind and adjust the pressure so that you end up with a bevel that has the correct angle and meets up with the prescribed target center line on the blanks blade edge. This is much easier said than done. Even experienced blade smiths can spend a lot of time chasing bevels. Keep in mind that grinding is all about time, pressure, and the grit of the belt. If you notice one area needs more grinding, you can spend more time in that area or just apply a little more pressure.
Knifemakers can also utilize a variety of bevel jigs to make grinding flat bevels easier. Most of these jigs secure the blade to the jig, in a bevel-up position, and then slide along a flat 90-degree work table. The jig is adjustable for the desired bevel angle. All the knifemaker has to do is secure the blade into the jig and then slide the jig across the belt grinders work table while applying steady pressure down and inward towards the belt. The jig has to be pivoted outward horizontally as the belt starts to grind the curved belly of the blade. This keeps the belt consistently in contact with the blade as the blade tapers to a point.
Another popular type of jig, or it may be better described as a work rest, is the Tilt Table. This unique table gives the knifemaker flexibility. It allows new blade smiths to quickly and easily produce beautiful flat bevels. The same table can then also be used for hollow grinds while giving the experienced knifemaker complete control of the blade. The table can be set at any desired bevel angle. The blade is not secured to the table but rather held against the table’s flat surface as the knifemaker slowly moves the blade up and into contact with the belt. The beauty of this system is it gives the knifemaker total control. He or she can watch the scribed lines and grind more in one area if needed. If the knifemaker carefully grinds a consistent line along the scribed marks, the bevel will have followed the curvature of the blade.
Blade smiths that freehand grind have also found the tilt table helpful. It allows them to establish a consistent rough pre-heat treatment bevel angle very quickly. After hardening, the blade smith hand holds the blade, resting the pre-established bevel directly onto the belt grinders platen or contact wheel. Besides the purchase of a 2x72 grinder, the tilt table would be our best recommendation for blades smiths looking to make the most significant improvement in the quality of the bevels they grind.
Full Flat Grind
Unlike flat bevels, a full-flat grind will not leave a bevel line. The blade will taper from the spine all the way to the edge of the blade. This type of bevel is often used for chef and kitchen knives. As with all bevels, start by scribing the railroad track center lines on the edge of the blade. Next, using a 90-degree work table, rest the spine of the knife on the table. Use a coarse grit belt to remove the majority of the material. The object is to break the corner first and grind a steep angle close to the scribed line. Next start to chase the bevel line or walk the bevel upward toward the spine of the blade. This is done by slightly adjusting the angle the blade is being held at. When the bevel line has been chased almost all the way up to the spine, you will be holding the blade almost completely flat against the grinders flat platen. Now, turn the blade tip down and attach a shop magnet. The magnet will act as a handle. Holding the magnet allows you to grind horizontally along the flat platen. Continue using progressively finer belts to obtain the surface finish desired. When moving the magnet to the other side of the blade use painter’s tape to prevent scratches from the magnet.
Hollow Ground Bevels
Hollow ground bevels are done on a large contact wheel instead of a flat platen. Hollow grinds can be done freehand or with a variety of jigs. The diameter of the hollow grind is determined by the size of the contact wheel. Historically, the most popular jigs are pressure jigs. They track perpendicular to the grinders belt. Pressure is created by turning a dial on the back of the jig which moves the blade forward into the belt. The blade smith inserts the blade and then pulls it across the grinders belt in a jig track. Pressure jigs can be designed for either edge up or edge down bevel grinding.
Another option is to use the same tilt table discussed during flat bevels. The height on the tilt table, as well as angle, can be adjusted. Creating beautiful hollow grinds is very much the same as grinding flat bevels on the tilt table. Parallel lines are scribed on the edge of the blade and then the blade smith carefully slides the blade up and into contact with the contact wheel while supporting the blade flat against the Tilt Table. One trick of the trade used when setting the tilt table up for hollow grinds is to scribe a piece of scrap wood with the same center line scribe preset for the thickness of the blade. Then, grind a bevel in the wood and see how it looks. You can then easily adjust the width of the bevel without having damaged a good piece of steel.